It is well established that the energy which enables the muscles in mammals to contract and expand is produced from adenosine triphosphate (ATP). The adenosine triphosphate metabolizes in the muscle by cleaving a phosphate radical to release the energy to contract the muscle and to produce adenosine diphosphate (ADP) as a byproduct. As the amount of adenosine triphosphate is depleted during extended exercise, muscle strength decreases and muscle fatigue increases.
Adenosine triphosphate can be produced in the muscle from glycogen or creatine phosphate. Creatine phosphate provides a ready source of phosphate and is able to resynthesize adenosine triphosphate at nearly twice the rate compared to glycogen. The amount of creatine phosphate in the muscle and the bloodstream are important in the time required to recover from muscle fatigue.
Creatine is produced naturally in humans and other animals and is converted to creatine phosphate in the muscles. The creatine phosphate is stored in the muscle as an available source of phosphate for the resynthesis of adenosine triphosphate from adenosine diphosphate.
Creatine is produced in the liver, kidney and pancreas and is supplied to the body by the food intake. Creatine is only sparingly soluble in water and is normally present in the bloodstream at a concentration of about 50 .mu.mol per liter of blood. The creatine enters the muscle tissue by active transport where it is converted to creatine phosphate. Muscle fatigue and the accumulation of lactic acid occur when the supply of creatine phosphate is exhausted and the adenosine diphosphate cannot be converted to adenosine triphosphate.
Numerous efforts have been made to increase the content of the creatine phosphate in the muscle to increase the muscle power and the ability to exercise longer. Creatine can be supplied to the body to enhance physical performance since the list of drugs prohibited by the International Olympic Committee, which includes more than 120 kinds, does not include creatine, which is an amino acid normally biosynthesized in vertebrates. For example, International Patent Publication No. WO 94/02127 discloses a method of increasing the creatine levels in the body by administering creatine orally, enterally or parenterally to an animal. However, creatine is generally not effectively administered orally in powder form since creatine rapidly converts to creatinine by the acidic conditions in the stomach, and is not in a soluble bioavailable form causing a disturbance in the positive osmotic pressure necessary for absorption. Creatinine is the inactive form of creatine which is quickly depleted from the body. Creatinine is not able to convert to creatine phosphate and does not participate in the regeneration of adenosine triphosphate and is excreted in the urine.
Creatine has also been used in aqueous solutions as a beverage which is intended to supply creatine to the body. Examples of beverages containing solubilized creatine are disclosed in U.S. Pat. Nos. 5,612,375 and 5,397,786. Other methods which do not use any heat have to be developed since heat was found to accelerate the conversion of creatine to creatinine. Creatine is only sparingly soluble in water so that the amount of creatine that can be supplied in solution is limited. In addition, acidic conditions in the stomach convert the creatine to creatinine, thereby reducing the amount of creatine available for absorption by the body. Heat and hydrogen ion concentration accelerate decomposition of creatine.
Accordingly, a continuing need exists in the industry and in athletic circles for an improved method of administering creatine and supplying creatine to the body in stable form.